Hitherto, various devices have been proposed as gas sensors having ceramic gas detecting elements. These gas sensors have gas detecting elements made of zirconia ceramics of oxygen ion conductivity, for example, and are installed in exhaust pipes of an internal-combustion engine for detecting the oxygen concentration in the emission (see, for example, patent document 1 and patent document 2).
[Patent document 1] Unexamined utility model application publication No. S53 (1978)-95884
[Patent document 2] Unexamined utility model application publication No. S53 (1978)-95886